1. Field of the Invention
The present invention refers to the production of droplets as required and is applicable especially to carrying out inkprojection printing.
2. Description of the Prior Art
Devices for producing drops as required are already known, which include at least one nozzle fed with liquid through a pipe connected to a tank of liquid and associated with a pressure transducer generating pulsations in the liquid. The pressure transducer which is generally tubular and of piezoelectric type surrounds the pipe in the vicinity of the nozzle. When it is excited by an electric voltage pulse it contracts and acts upon the liquid by way of the pipe, the pressure wave thus created expelling a droplet out of the orifice of the nozzle.
In a device of this species, described, for example, in the French Pat. No. 75 38 342 (Pub. 229485o), it is necessary to provide means for preventing the arrival of air bubbles in the nozzle, which would disturb its operation. In the aforesaid Patent Application a capillary filter means is employed for the purpose.